This invention relates to a hybrid Diesel fuel composition.
It is highly desirable that such hybrid Diesel fuel compositions be stable microemulsions, that is to say, that they may undergo a number of manipulations such as pumping, storage and other like operations with a minimum hazard of splitting of such microemulsions.
In order to overcome economic problems originated by the petroleum product crisis, hybrid Diesel fuel compositions have been suggested recently, which contained a fraction of alcohols, mainly methanol and ethanol.
These additions, however, have created technical problems, mainly connected with the intolerance to water, phase splitting and unsatisfactory rheological properties.
Thus, for example, methanol is inherently insoluble in the Diesel fuels, while ethanol can be blended in any proportions with Diesel fuels, but even tiny amounts of water suffice to bring about phase splitting.
The technical problem at stake was then that of providing hybrid Diesel fuel compositions which were less water-incompatible, on bearing in mind, also, the circumstance that water is a Diesel-fuel improver, in that it lowers the combustion temperature and reduces both the emission of fumes and the formation of nitrogen oxides.
U.S. Pat. No. 4,451,267 has suggested to use a surface-active agent, or a blend of such agents, in order to improve Diesel fuel compositions containing a conventional Diesel fuel, lower alcohols and water.
EP-A- 0 117 915 has suggested not to use surface-active agents, but, rather, to adopt higher alcohols to stabilize blends of conventional Diesel fuel, lower alcohols and water.
These approaches, however, have proven to be not entirely satisfactory because comparatively high amounts of surface-active agents are required to stabilize the emulsions or microemulsions satisfactorily, and, on the other hand, if no surface-active agents are used, the amounts of higher alcohols required are, again, comparatively high and this is an added cost.
With either approach, however, both in the case of homogeneous blends and (micro)emulsions, the water compatibility generally leaves much to be desired in order to achieve a satisfactory combustion with reduced emission of fumes and nitrogen oxides.